(1) Field of the Invention
This invention relates generally to apparatus and methods for suspending and remotely manipulating a solid in a fluid by means of ultrasonic waves. More specifically, one aspect of the invention relates to an apparatus and method which applies ultrasonic bubble manipulation techniques to a solid material containing a predetermined region of encapsulated gas bubbles to remotely manipulate that solid within a fluid. In another aspect of the invention, the same ultrasonic bubble manipulation techniques are applied to manipulate such a solid in a fluid flow tunnel, and to measure hydrodynamic drag of the solid under varying flow conditions.
(2) Brief Description of the Prior Art
In the development of undersea vehicles it is highly advantageous to be able to test the vehicles hydrodynamic characteristics in fluid flow conditions prior to actual construction of a prototype vehicle. In this regard, small scale models of new vehicles are usually suspended within a fluid flow duct, i.e., water tunnel, and evaluated for their fluid flow properties. Typical methods of suspending the models within the fluid flow tunnel include wires, strings or struts which physically suspend the vehicles position within the fluid flow. While this method of testing provides valuable information, the introduction of large supporting objects into the fluid flow alters the flow of the fluid through the duct and thus alters the results that are obtained. It is impossible to completely escape this problem as long as a foreign object is in the flow.
At present, there are few means available to effectively suspend or manipulate the position of a solid in a fluid without physically attaching to the object. Existing nonphysical suspension methods, such as using an electric or magnetic field to manipulate positions of solids have serious shortcomings. The basic problem is that in order to exert large forces via magnetic and electric fields, it is desirable to be as close as possible to the object. Thus, to suspend an object in a fluid via magnetic fields, a magnet or the equivalent would have to be near the object in the fluid, or very near a boundary of the fluid. Either case is undesirable since the location of the magnet near the solid, or the location of the solid body near the wall of the fluid flow tunnel will obviously alter the fluid flow near the solid body.
Accordingly, there is a serious need for an effective method for suspending and remotely manipulating solids in a fluid flow without physically exerting control over the solid or introducing physical supporting structures into the fluid flow chamber. Furthermore, there is also a need for an apparatus and method for effectively measuring drag within a fluid flow without affecting fluid flow or operation of the water tunnel.